The purpose of this project is to understand the pathogenesis of autoimmune disease in mammalian systems by studying the model of New Zealand Mice. The present areas of investigation are the early activation of the immune system, manifested by macrophage activation and immunoglobulin production; B and T cell membrane receptors and differentiation antigen abnormalities; and the regulation of xenotropic murine leukemia virus production and virus coded cell surface antigens. The genetic analysis of these parameters has identified several separate genes which presumably contribute to the development of autoimmune disease.